1. Field of the Invention
The present invention relates to an apparatus for shaping a workpiece of a superplastic metal through superplastic deformation with a pressurized gas while the plate is being heated.
2. Description of the Prior Art
One known apparatus for shaping a superplastic metal plate is disclosed in Japanese laid-open utility model publication No. 2-87513, for example.
The disclosed shaping apparatus has an upper shaping die and a lower shaping die which hold a superplastic metal plate therebetween. The superplastic metal plate between the upper and lower shaping dies is heated by heaters that are embedded respectively in the upper and lower shaping dies. While the superplastic metal plate is being thus heated a pressurized gas is introduced into a cavity defined in the upper and lower shaping dies, thereby deforming the superplastic metal plate to a desired shape along a shaping surface of the cavity.
However, since the heaters are embedded in the upper and lower shaping dies, the upper and lower shaping dies are required to be thick enough to be durable for increased mechanical strength. Consequently, the upper and lower shaping dies are necessarily large in size, and so are a device for clamping the upper and lower shaping dies (i.e., a device for vertically moving the upper die), the heaters, and thermally insulating members for preventing the upper and lower shaping dies from radiating heat.
When shaped products of a different type or configuration are to be produced, the large shaping dies need to be replaced with corresponding shaping dies, and the heaters and the thermally insulating members also need to be replaced with corresponding heaters and thermally insulating members. Therefore, the conventional shaping apparatus is relatively expensive to manufacture and costly to operate.